PITTSBURGH — Cam Heyward knows better than to get ahead of himself. Sure, the Pittsburgh Steelers’ run defense was better last week against Baltimore, when the Ravens needed 29 carries to manage 50 yards.

Then again, considering how ineffective it was in losses to Miami and New England — losses Heyward missed due to a hamstring injury — it’s a backhanded compliment at best. And Pittsburgh’s defensive captain knows it.

“It’s a start,” Heyward said Thursday. “We know we’ve got a bigger challenge.”

Maybe the biggest in the NFL.

The guy in the backfield on Sunday won’t be any nameless, starless Ravens but Dallas rookie Ezekiel Elliott, who leads the league in rushing at the halfway point and has established veterans such as Heyward grasping for superlatives.

“He’s had a lot of success,” Heyward said. “He can cut when he needs to. He can jump when he needs to. If a play doesn’t work out his way, he’s not afraid to jump out and challenge your corners.”

And just about anything else that gets in his way. The 21-year-old is averaging 5.0 yards per carry and hardly seems ready to hit the wall halfway through the 16-game slog that is the regular season. Some of his production is due to playing behind one of the NFL’s best offensive lines. Not all of it, though. There’s more than a hint of tenacity to go with Elliott’s natural speed and power.

“His feet don’t go dead,” Steelers defensive coordinator Keith Butler said.

Meaning they keep churning even as Elliott finds himself enveloped by tacklers. On an 8-yard touchdown sprint last week against Cleveland, he stepped out of a tackle at the 10 and darted to the end zone. Later on, he caught a pass in the flat and was stood up almost immediately by Browns defensive back Tramon Williams, only to bounce off the slip through the arms of Brian Boddy-Calhoun to turn a short loss into a 5-yard gain in a 35-10 romp that pushed the Cowboys’ to an NFC-best 7-1.

Pittsburgh linebacker Ryan Shazier, a former teammate of Elliott’s at Ohio State, likened Elliott to NBA star Dwyane Wade.

“He’s like a slasher runner,” Shazier said. “When he needs to hit the hole, he hits the hole. When he needs to make three (yards), he makes three.”

Though typically he springs for considerably more than that. Elliott already has seven runs of 20 yards or more, tops in the league. And the player who routinely turns to the sideline and mimics a kid frantically scarfing down a bowl of Lucky Charms (Elliott’s sign language for “keep feeding me”) hardly seems winded despite being on pace for more than 350 carries.

“It’s kind of weird just to feel that we’re only halfway through, coming from college where the season starts earlier and it’s shorter, so it feels a little bit different,” Elliott said. “But it’s important to maintain that routine so your body doesn’t break down so you can stay fresh.”